Have not had any problem since using the humane traps I linked earlier, which caught whole groups/families at a time. Of course, I have a lot more wildlife now since, unlike the previous owner, I don't sit on the deck and shoot every critter that enters the yard. Now I have red foxes, silver foxes, bobcats, coyotes of course (mine are super wild--I have never seen one!), three kinds of owls, broad-winged hawks, falcons, and 5 skunks that enter the yard every evening and diligently scavange the yard--all potential mouse predators. Also have no dogs/cats to scare wildlife away. So maybe all that helps.
I also cleaned up the yard so as to not provide any mouse hidey-holes near the house (wood piles, garden follies, and other junk). To get to the house they have to cross bare lawn.
Re specifically tractor storage, some guys who collect antique cars create barrier around the vehicle using metal flashing; one side can be folded down so you can drive out.